INFLUENCE OF HOT WOKKING ON STEEL.
dimensions of the test-piece, but Table XIV-B, which is free from this error, proves that the plates made from the large sizes hare a higher tensile strength and greater ductility.
Average Physical Results on Different Thicknesses of Steel Plates Without Eegard to Size of Ingots; there being an Equal Number of Plates of each Thickness Eolled from Each Sized Ingot.*
Thickness of plate. Ultimate strength; Ibs. per square in. Elongation in 8 inches ; per cent. Reduction of area; per cent. Annealed, ultimate strength; pounds per Square inch.
One inch. . . . One-half inch . One-quarter in. 62037 64584 69642 24.40 24.71 22.86 40.20 44.85 42.69 50416 61018 62980
Average Physical Eesults on Plates from Different-Sized Ingots Without Regard to Thickness of Plate; there being the same Number of each Thickness Rolled from a Given Size.*
Size of ingot; in inches. Thickness of slab in inches. Ultimate strength; Ibs. per square inch. Elongation in 8 inches ; per cent. Reduction of area; per cent. Annealed ultimate strength; pounds per square inch.
24x15 14x14 18x12 18x12 12x6 8' 8 8 4 4 66155 65296 65128 65520 64923 24.14 23.91 • 23.77 23.68 23.68 45.79 44.13 41.38 40.00 41.58 62197 62571 60461 60461 60018
Thus these experiments which were heralded as upsetting current beliefs are found to vindicate them; they do prove that in some cases very good results may be obtained by skillful manipulation under a bad system; but manufacturers have long since learned that a large amount of reduction is essential to secure reliable results in regular practice, and no short series of tests can upset this well-established facts
SEC. XIVc.—Amount of work necessary.—Up to within a comparatively recent period it was a common practice in America to roll plates directly from the ingot in one heat. This was unsatisfactory for more than one reason. First, the rolling of thin plates involved either the making of small ingots, which was objectionable and costly, or it involved rolling them from a large ingot, which
* From data in Journal I. and S.-J.j Vol. I., 1887, p. 121, et »cq.